This invention relates generally to electrical power generators and more particularly, to methods and systems for testing electrical components in electrical power generators.
In at least some known generators, a stator yoke in the generator surrounds an armature core and partially encloses a plurality of armature windings, which are sometimes referred to as stator windings or stator bars. At least some known stator windings are formed with a plurality of copper conductors that are wound in the armature to form loops. More specifically, the armature windings are arranged in such a manner to enable a desired voltage and current characteristics to be generated during operation. A plurality of hollow individual conductors, or strands inside the stator bars enable cooling water to be channeled within the stator bars.
Electrical insulation is wrapped around the stator bars electrically to isolate the stator bars from each other. The insulation facilitates preventing arcing between the windings, and also shields the bars from foreign objects that could electrically short the bars. However, the insulating properties of the insulation may degrade if the insulation becomes damp or is damaged. Voltage arcs may occur from the armature bars through degraded regions or wet regions of the insulation. Over time, continued operation with arcs may prematurely shorten the useful life of the generator.
To facilitate extending the useful life of the generator, the stator bars may be periodically tested. Within at least some known tests, groups of stator bars are “tied together” electrically and tested as a set, while the remaining bars are electrically grounded. More specifically, insulation is used to isolate the groups under test from the groups that are grounded to prevent electrical discharge or arcing between these groups. During at least some known tests, high-voltage blankets fabricated from rubber are positioned between the groups to facilitate electrically isolating adjacent groups from one another. However, known blankets may be difficult to use because of their size, shape, and weight, and may frequently not prevent arcing. When arcing occurs, the test is considered a failure and is stopped to prevent damage to the generator. Additional insulation is then installed in the area of the arcing and the test is re-performed. The process may need to be repeated several times before a successful test for the group under test may be performed at the required voltage level.